The story begins with Ayase Jiro, a young man who has been a NEET for two years after a bad experience with a black company. He makes a living by selling antiques and used goods online, a hobby that has become surprisingly lucrative. While exploring the dusty storage room of an old house, he stumbles upon a large, ornate mirror. While examining it, he trips and falls into the mirror, finding himself in a dark, stone-walled room. This room contains only a wooden chest, which, upon opening, reveals a set of medieval-style clothing. Jiro, after a brief moment of curiosity, returns through the mirror to his own world, contemplating the mirror's potential value.
Driven by his entrepreneurial spirit, Jiro negotiates with the elderly owner of the house and manages to acquire the mirror for a mere 4,000 yen, which the owner readily dismisses as unwanted junk. Back home, Jiro decides to investigate the mirror further, despite the inherent risks. He enters the mirror world again, this time equipped with a flashlight and boots. He finds a stone staircase leading upwards, which opens into a dilapidated Western-style mansion. Exploring the mansion, he discovers it is completely overgrown and abandoned, suggesting it's in a remote, undeveloped area. Venturing further, he finds a small village of stone houses and observes a farmer. To his surprise, the farmer and his wife speak Japanese, though Jiro's ears initially perceive it as an unknown language that his brain instantly translates.
Returning to the mansion, Jiro continues his search for information. He finds no books but notes the presence of valuable antique furniture. His attention is then drawn to a massive spider on the wall, which he photographs. Researching online, he determines the spider is unlike any known species, leading him to conclude he is not on Earth, but in another world. He decides to sell the mirror and the "right to travel" to this new world, planning to profit immensely. He retrieves the medieval clothing from the mirror world, finding it fits him well.
Upon re-entering the mirror world, Jiro notices two moons in the sky, confirming its otherworldly nature. He encounters a hunter named Shero Roth, who mistakes Jiro for an escapee from the inland. Shero, a former mercenary, and his wife Rebecca, also a former mercenary, offer Jiro hospitality. They explain that this world is the Hanook Empire's territory, specifically near the free city of Elishe, which allows trade with other nations. They also reveal the existence of "monsters" that emerge from areas with high concentrations of "magic essence," often found in dungeons or near dragons, and that these monsters are drawn to strong magical energy. They also mention the danger of "wild animals" like beastmen, who are known to harm humans.
Jiro is invited to Shero and Rebecca's home and learns more about their world. He is particularly fascinated by a beautifully crafted dagger, which Rebecca reveals was a gift from the Emperor to their former mercenary leader. Jiro is then encouraged to seek a "calling" or "job" through a blessing ceremony at a temple. During the ceremony, he is blessed by the Great Spirit Le Baraka and discovers he possesses an astonishing eight common callings (Swordsman, Wizard, Blacksmith, Craftsman, Trickster, Trader, Cook, Gemologist) and three unique callings: "The Library" (Otherworld Sage), "The Journey" (Principle of the World, True Mirror), and "The Judgment." He keeps his unique callings a secret, fearing unwanted attention.
Shero and Rebecca help Jiro register as a resident of Elishe, using a fabricated story of him being Rebecca's nephew who lost his memory and his referral letter. Jiro is given a Guild Card, which serves as his resident permit and allows him to conduct business. He also learns about the world's currency system: copper, silver, and gold coins. He sells some of his handmade knives to a merchant named Toby, earning him 10 gold coins, a significant sum. He also gives Shero his Bowie knife as a gift, which triggers a quest completion for Shero and results in Jiro receiving a "Spirit Stone" and Shero receiving one as well, indicating their encounter was part of a divine "guidance."
Overwhelmed by the events and his own deceptions, Jiro flees back to his own world, leaving Shero and Rebecca behind. Back in his room, he contemplates his next steps, which include investigating the value of the gold coins and the Spirit Stone, and potentially exploring the possibility of finding elves, inspired by the elf priestess he met. He also decides to create an online thread on a Japanese forum to document his experiences, sharing photos of the giant spider and the mirror world. He then begins to research the value of the gold coins, discovering they are pure gold and worth a considerable amount. He sells one gold coin for 154,000 yen, solidifying his decision to pursue trade between worlds.
